1. Field of the Invention
The present invention relates to a webbing take-up device which tenses a webbing in a direction of restraining a vehicle occupant at the time of rapid deceleration of a vehicle, and in particular, to a webbing take-up device which, at the time of impeding pulling-out of a webbing, can absorb energy while allowing the webbing to be pulled-out.
Further, the present invention relates to a vehicle equipped with this webbing take-up device.
2. Description of the Related Art
In a webbing take-up device, at the time of rapid deceleration of a vehicle, rotation of a spool (take-up shaft) in a webbing pull-out direction is locked such that pulling-out of the webbing is impeded. As this locking mechanism, a lock member is provided in a vicinity of a device frame at one end side of the spool. Due to this lock member being operated when the vehicle rapidly decelerates, rotation of the spool in the webbing pull-out direction is hindered.
Further, in such a webbing take-up device, at the time of impeding pulling-out of the webbing, a predetermined amount of pull-out of the webbing is permitted and energy is absorbed. There are devices in which, for example, a spool and a torsion bar disposed coaxially with the spool form the energy absorbing mechanism. Generally, the torsion bar is connected to a lock base and the spool such that the torsion bar and the lock base and the spool do not rotate relative to one another. One end portion of the torsion bar is connected to the spool, and the other end portion of the torsion bar is connected to a lock base to which a lock member is connected. The spool and the lock base usually rotate integrally via the torsion bar. However, at the time of a rapid deceleration of the vehicle, in a state in which rotation of the lock base in the webbing pull-out direction is hindered, the spool rotates in the webbing pull-out direction with respect to the lock base due to the webbing tensile force. At this time, the torsion bar twists, energy is absorbed, and a predetermined amount of rotation of the spool is permitted. The absorbed energy is determined by the product of the load applied to the webbing (the force limiter load) and the webbing pull-out amount (the amount of rotation of the spool). In the webbing take-up device, the force limiter load and the allowed amount of rotation of the spool (the limit of twisting of the torsion bar) are applied.
However, in such a conventional webbing take-up device, the force limiter load at the time of energy absorption is governed by the values of the properties of the material of the torsion bar and the dimensional configuration of the torsion bar. The force limiter load is a fixed value regardless of, for example, the inertial energy of the vehicle occupant such as the collision energy whose parameters are the weight and the physique of the vehicle occupant, the vehicle speed at the time of the collision and the like. Further, the force limiter load is a fixed value from the beginning to the end of energy absorption. Namely, in a conventional webbing take-up device, both during rapid deceleration of the vehicle and during the process of energy absorption, different force limiter loads cannot be selected.
However, if the force limiter load can be reduced (if a small force limiter load can be selected) at an appropriate time in the energy absorbing process, the webbing pull-out amount (the amount of movement of the vehicle occupant) can be suppressed by, at the initial stage of rapid deceleration of the vehicle, applying a large force limiter load so as to make the energy absorption amount per spool rotation amount (webbing pull-out amount) large. On the other hand, after a predetermined energy absorption (after a predetermined amount of energy has been absorbed), by reducing the force limiter load, the load applied to the vehicle occupant can be decreased.
In particular, in a vehicle equipped with an air bag device, by reducing the force limiter load immediately before contact of the air bag and the vehicle occupant, the total load applied to the vehicle occupant can be reduced, and there is less possibility that the vehicle occupant is injured, compared to the conventional device.
A webbing take-up device in which different force limiter loads can be selected in accordance with the inertial energy of the vehicle occupant has been contemplated. However, in order to be able to change the force limiter load in such a conventional webbing take-up device, for example, plural torsion bars are provided and combination of torsion bars which absorbs energy is changed, or torsion bars of different diameters are combined coaxially and the energy absorbing positions thereof are changed. Thus, these structures are complex.
In view of the aforementioned, a first object of the present invention is to provide a webbing take-up device which, with a simple structure, can select different force limiter loads at arbitrary times.
A second object of the present invention is to provide a vehicle which is equipped with the aforementioned webbing take-up device and an air bag device, and which can reduce the load applied to a vehicle occupant.
In order to achieve the above-described first object, a first aspect of the present invention is a webbing take-up device comprising: a cylindrical spool at which a webbing is taken-up and from which a webbing is pulled-out; a lock base provided at one end side of the spool so as to be coaxial with the spool and so as to be able to rotate relatively to the spool; a locking member which is connected to the lock base and which impedes rotation of the lock base in a direction of pulling out the webbing by engaging with a frame at a time when a predetermined acceleration is sensed; a torsion bar which is provided within the spool coaxially with the spool, one end of the torsion bar being connected to the spool, another end of the torsion bar being connected to the lock base, the torsion bar making the spool and the lock base rotate integrally in a normal state, and a state in which rotation of the lock base in the direction of pulling out the webbing is impeded by the locking member, the torsion bar being twisted due to webbing tensile force while making the spool rotate relatively with respect to the lock base in the direction of pulling out the webbing; at least one wire whose one end portion is fixed to the lock base and whose other end portion and an intermediate portion are inserted in the spool, and due to the at least one wire being pulled out from the spool at a time when the spool rotates relatively with respect to the lock base, the at least one wire generating a resistance force; and a cutting section which is able to cut the at least one wire at an arbitrary time.
The wire of the first aspect may be a rod-shaped member which does not easily deform (e.g., which does not deform by its own weight or due to force which can be applied by a human).
In the webbing take-up device of the first aspect, the spool and the lock base are connected via the torsion bar, and usually the spool and the lock base rotate integrally. Thus, usually, the webbing can be freely taken-up and pulled-out.
When the vehicle rapidly decelerates, the lock member operates to impede rotation of the lock base in the webbing pull-out direction. At this time, the webbing tensile force accompanying the inertial movement of the vehicle occupant is applied, via the spool, to the torsion bar as rotational force in the webbing pull-out direction. As a result, the spool rotates relatively to the lock base while the torsion bar is twisted. Further, when the spool begins to rotate relatively to the lock base, along with this rotation, the wire is pulled out from the spool while being drawn through (rubbed) at an exit portion of the spool, and is taken-up on the side surface of the lock base. In this way, while the twisting load of the torsion bar and the drawing-through (rubbed) load of the wire are applied to the webbing (the vehicle occupant) as a constant force limiter load, the spool rotates in the webbing pull-out direction with respect to the lock base, the webbing is pulled-out, and energy is absorbed.
Moreover, when the cutting section is operated at an arbitrary time in the energy absorbing process, the wire is cut by the cutting section. In this way, only the twisting load of the torsion bar is applied to the webbing as the force limiter load, and the force limiter load can be reduced at an arbitrary time.
Accordingly, at the initial stages of rapid vehicle deceleration, by applying a large force limiter load such that the energy absorbing amount per rotational amount of the spool (webbing pull-out amount) is large, the webbing pull-out amount (amount of movement of the vehicle occupant) can be suppressed. On the other hand, after a predetermined energy absorption, by reducing the force limiter load, the load applied to the vehicle occupant can be reduced.
In a case in which the cutting section is not operated, a large force limiter load is maintained throughout the entire energy absorption process. In a case in which the cutting section is operated immediately after rapid deceleration of the vehicle (for example, at substantially the same time of beginning of the rapid deceleration of the vehicle), a small force limiter load is applied from the initial stages of rapid deceleration of the vehicle. As a result, switching can be carried out between two different force limiter loads in accordance with the inertial energy of the vehicle occupant which is based on the physique of the vehicle occupant and the type of collision.
In this way, in the webbing take-up device relating to the first aspect of the present invention, different force limiter loads can be selected at arbitrary times with a simple structure.
In a webbing take-up device relating to a second aspect of the present invention, the cutting section in the webbing take-up device of the first aspect has: a cutting gear which is formed in a disc shape having meshing teeth at an outer peripheral portion thereof and which has a cutting hole in a disc side surface, the cutting gear being disposed between the spool and the lock base so as to be freely rotatable and so as to be coaxial with the spool, with the at least one wire inserted through the cutting hole; and driving section having driving teeth which can mesh with the meshing teeth of the cutting gear, the driving section usually allowing the cutting gear to rotate freely, and due to the drive means being operated, the drive teeth moving while meshing with the meshing teeth of the cutting gear such that the driving section forcibly rotates the cutting gear with respect to the spool and the lock base.
In the webbing take-up device of the second aspect, a wire is inserted through a cutting hole formed in a disc side surface of a cutting gear provided, so as to be freely rotatable, between the spool and the lock base. One end portion of the wire is fixed to the lock base, whereas the intermediate portion and the other end portion of the wire are inserted into the spool. Thus, usually, the spool and the lock base, which are connected via the torsion bar, and the cutting gear rotate integrally via the wire. As a result, usually, the wire is not cut.
When the driving section is operated at an arbitrary time, due to the driving teeth of the driving section moving while meshing with the meshing teeth of the cutting gear, the cutting gear is forcibly rotated. The cutting gear is set between the spool and the lock base in a state in which the wire is inserted through the cutting hole provided in the disk surface of the cutting gear. Thus, when the cutting gear is rotated forcibly with respect to the spool and the lock base, the wire is cut by the cutting hole provided at the cutting gear.
Accordingly, the force limiter load can be reduced at an arbitrary time.
In this way, in the webbing take-up device of the second aspect, different force limiter loads can be reliably selected (switched) at arbitrary time with a structure that is even more simple.
In order to achieve the above described second object, a third aspect of the present invention is a vehicle comprising: (a) a webbing take-up device having: a cylindrical spool at which a webbing is taken-up and from which a webbing is pulled-out; a lock base provided at one end side of the spool so as to be coaxial with the spool and so as to be able to rotate relatively to the spool; a locking member which is connected to the lock base and which impedes rotation of the lock base in a direction of pulling out the webbing by engaging with a frame at a time when a predetermined acceleration is sensed; a torsion bar which is provided within the spool coaxially with the spool, one end of the torsion bar being connected to the spool, another end of the torsion bar being connected to the lock base, the torsion bar usually making the spool and the lock base rotate integrally, and in a state in which rotation of the lock base in the direction of pulling out the webbing is impeded by the locking member, the torsion bar twisting due to webbing tensile force while making the spool rotate relatively with respect to the lock base in the direction of pulling out the webbing; at least one wire whose one end portion is fixed to the lock base and whose other end portion and an intermediate portion are inserted in the spool, the wire being pulled out from the spool at a time when the spool rotates relatively with respect to the lock base, the at least one wire generating a resistance force; and a cutting section which is able to cut the at least one wire at an arbitrary time; (b) an air bag device; (c) a sensor which can detect information relating to at least one of a vehicle occupant and a state of the vehicle; and (d) control section which is connected to the cutting section and the sensor, and which can operate the cutting section on the basis of detection results of the sensor.
The sensor of the third aspect is not only a sensor which directly senses the distance between the bag body and the vehicle occupant, but also may be an indirect sensor system (program) which can compute the distance between the bag body and the vehicle occupant on the basis of the results of detection of sensor(s) already provided in the vehicle (e.g., a seat load sensor, an acceleration sensor, a webbing take-up amount sensor, or a combination of these sensors).
In the vehicle of the third aspect, for example, the vehicle is provided with the sensor which is able to detect a distance between a bag body of the air bag device and the vehicle occupant, and control section which is connected to the cutting section and the sensor electrically and which can operate the cutting section when it is judged there is a state immediately before contact of the bag body and the vehicle occupant on the basis of detection result of the sensor, when the air bag device is activated, the sensor detects the distance between the bag body and the vehicle occupant, and outputs the results of detection to the control means. When the control means, to which the results of detection of the sensor have been inputted, judges, on the basis of the results of detection, that there is a state immediately before contact of the bag body and the vehicle occupant, the control means operates the cutting section.
In this way, immediately before contact of the bag body and the vehicle occupant, the force limiter load is reduced. Thus, in the state immediately before contact of the bag body and the vehicle occupant, a large force limiter load is applied, the energy absorption amount per time is made large, and the pull-out amount of the webbing (amount of movement of the vehicle occupant) can be suppressed. On the other hand, after contact of the bag body and the vehicle occupant, a smaller force limiter load is applied such that the force applied to the body of the vehicle occupant from the exterior is reduced. In this way, there is less possibility that the vehicle occupant is injured, compared to the conventional device.
In accordance with the physique of the vehicle occupant and the state of the collision, for example, in a case in which the inertial energy of the vehicle occupant is large, it is possible to not operate the cutting section, such that even after contact of the bag body and the vehicle occupant, a large force limiter load may be applied. On the other hand, in a case in which the inertial energy of the vehicle occupant is small, the cutting section can be operated before operation of the air bag device, and a small force limiter load can be applied from before contact of the bag body and the vehicle occupant.
In this way, the vehicle of the third aspect of the present invention is equipped with the above-described webbing take-up device and an air bag device, and the load applied to the vehicle occupant can be reduced.
A fourth aspect of the present invention is a webbing take-up device comprising: a cylindrical spool at which a webbing is taken-up and from which a webbing is pulled-out; a lock base provided at one end side of the spool so as to be coaxial with the spool and so as to be able to rotate relatively to the spool; a locking member which is connected to the lock base and which impedes rotation of the lock base in a direction of pulling out the webbing by engaging with a frame at a time when a predetermined acceleration is sensed; a torsion bar which is provided within the spool coaxially with the spool, one end of the torsion bar being connected to the spool, another end of the torsion bar being connected to the lock base, the torsion bar making the spool and the lock base rotate integrally in a normal state, and in a state in which rotation of the lock base in the direction of pulling out the webbing is impeded by the locking member, the torsion bar being twisted due to webbing tensile force while making the spool rotate relatively with respect to the lock base in the direction of pulling out the webbing; at least one wire whose one end portion is fixed to the lock base and whose other end portion and an intermediate portion are inserted in the spool, and due to the at least one wire being pulled out from the spool at a time when the spool rotates relatively with respect to the lock base, the at least one wire generating a resistance force; and a cutting section which is able to cut the at least one wire at an arbitrary time, wherein the cuffing section has: a cutting gear which is formed in a disc shape having meshing teeth at an outer peripheral portion thereof and which has a cuffing hole in a disc side surface, the cutting gear being disposed between the spool and the lock base so as to be freely rotatable and so as to be coaxial with the spool, with the at least one wire inserted through the cutting hole; and a driving section having driving teeth which can mesh with the meshing teeth of the cutting gear, the driving section allowing the cutting gear to rotate freely in the normal state, and due to the drive means being operated, the drive teeth being moved while meshing with the meshing teeth of the cutting gear such that the driving section forcibly rotates the cutting with respect to the spool and the lock base.
In a fifth aspect of the present invention, in the webbing take-up device of the first or the fourth aspect, the intermediate portion and the other end portion of the wire are accommodated in a wire accommodating portion provided at the spool.
In a sixth aspect of the present invention, in the webbing take-up device of the fifth aspect, the wire accommodating portion is a hole which is substantially parallel to an axis of rotation of the spool.
In a seventh aspect of the present invention, in the webbing take-up device of the fifth aspect, the wire accommodating portion is formed in spiral shape with respect to an axis of rotation of the spool.
In an eighth aspect of the present invention, in the webbing take-up device of the fifth aspect, a plurality of the wires and a plurality of the wire accommodating portions are provided.
In a ninth aspect of the present invention, in the vehicle of the third aspect, the sensor is a sensor which can detect a distance between the vehicle occupant and a bag body of the air bag device.
In a tenth aspect of the present invention, in the vehicle of the third aspect, the sensor is a sensor which can detect at least one of a weight of the vehicle occupant and a physique of the vehicle occupant.
In an eleventh aspect of the present invention, in the vehicle of the third aspect, the sensor detects a running state of the vehicle.